The present invention generally relates to telecommunication techniques. More particularly, the present invention relates to a method and system for allocating bandwidth and power resources for a wireless network user. More specifically, embodiments of the present invention provide a method and system for optimal allocation of bandwidth and power resources to voice-on-internet protocol (VoIP) channels in the forward link of wireless networks using orthogonal frequency domain multiple access (OFDMA) technology. But it would be recognized that the invention has a much broader range of applicability.
Orthogonal Frequency Domain Multiple Access (OFDMA) technology is a multi-user version of the popular Orthogonal Frequency-Division Multiplexing (OFDM) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users, allowing simultaneous low data rate transmission from several users. Based on feedback information about the channel conditions, adaptive user-to-subcarrier assignment can be achieved. If the assignment is done sufficiently fast, this further improves the OFDM robustness to fast fading and narrow-band cochannel interference, and makes it possible to achieve even better system spectral efficiency. Fourth Generation wireless networks will use OFDMA technology in order to provide the high throughput and low latency required for present and future wireless applications.
In a forward link of an OFDMA network, each traffic and control channel within a frame must be allocated power, bandwidth (number of subcarriers) and time (number of OFDMA symbols) resources. This flexibility is one of the advantages of OFDMA but requires more sophisticated resource management than Third Generation networks. Some conventional approaches have focused on the scheduling of power and bandwidth resources over OFDMA channels. Typically, each Subscriber Station (SS) needs to be informed of the bandwidth allocations each time the SS is served. In this way one can take advantage of fast fading and serve users during positive fades. However, such approaches are limited for delay tolerant data traffic and only a subset of users are served at a time.
When the network starts to deal with delay sensitive traffic with near constant bit rate such as VoIP, since all users must be served sufficiently fast to maintain low latencies, signaling resources (needed to indicate which frame resources are meant for which user) can become a significant burden. VoIP is presently supported by allocating a subset of diverse subcarriers to each active voice connection. Then a closed loop power control is used to maintain the frame error rate (FER) at the desired level as is done in traditional CDMA 1X networks. The number of available VoIP channels is fixed and any new connection request is queued if no channels are available. The queuing must be limited to a relative small value otherwise the end to end delay performance would be not acceptable for maintaining the audio stream even with a sizeable buffer.
As seen above, an improved approach by dynamically changing the bandwidth resources over time in addition to changing the power resources for optimally allocating both bandwidth and power to OFDMA VoIP channels is desired. Particularly, an algorithm for obtaining optimal discrete bandwidth allocation as optimal power is achieved for a user channel should provide further system efficiency increase and performance improvement.